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Using STORAGE Function


IBM Mainframe Forums -> CLIST & REXX
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angt

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PostPosted: Wed Aug 27, 2008 1:06 am
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Hi

I am trying to use STORAGE function of rexx to override a value at given adress but it is returning null string all the times.

Storage(address,,data) , when i remove data from the function it returns first byte at that place but as soon as i put data it returns null string

Please enlightem me if you have any idea about it

thanks
Anurag
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dick scherrer

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PostPosted: Wed Aug 27, 2008 1:23 am
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Hello,

It will probably help if you post the code. Please use the "Code" tag on the Reply panel.

When you have a question, please start a new topic for your question rather than posting a reply to some inactive topic.
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expat

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PostPosted: Wed Aug 27, 2008 11:38 am
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Are you trying to update protected storage ?
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angt

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PostPosted: Wed Aug 27, 2008 5:46 pm
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Here is the code

Code:
/* REXX GETRC                        */       
                                             
NUMERIC DIGITS(32) /*ENSURE MAX PRECISION*/   
TCB = PTR(540,4)                             
TIOT= PTR(TCB+12,4)                           
JNAM= STG(TIOT,8)                             
SAY 'JOB NAME:' JNAM                         
TRACE I                                       
JNAM1 = STG(TIOT,,'ABCDEFG')                 
JNAM1 = STG(TIOT,8)                           
SAY 'JOB NAME:' JNAM ' ' JNAM1               
EXIT(0)                                       
TRACE OFF                                     
PTR: RETURN C2D(STORAGE(D2X(ARG(1)),ARG(2))) 
STG: RETURN STORAGE(D2X(ARG(1)),ARG(2),ARG(3))
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expat

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PostPosted: Wed Aug 27, 2008 7:10 pm
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I think that you will find that only APF authorised programs, which are usually under the control of the sysprogs and closely monitored by the security people, are allowed to update storage in flight.

That is what I found out when trying to update a storage location with REXX myself.
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angt

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PostPosted: Wed Aug 27, 2008 7:18 pm
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Thanks Expat,

Can you show me some other examples where I can check that storage works

angt
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expat

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PostPosted: Wed Aug 27, 2008 7:37 pm
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Not that I know of. Updating storage on the fly isn't really part of my job function, and I only tried it out a few times when there was nothing much else to do.

The function quite happily retrieves data from the given location, but does not update it.

Might have a play with the SAS equivilent of PEEK and POKE, but then again that all depends on time availability.
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Pedro

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PostPosted: Wed Aug 27, 2008 10:06 pm
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<good Pedro>
You should just submit the job with a correct name! Why would you want to change the name after submitting? You cannot update system control blocks, but should be able to update your private storage.

You can use IPCS to find control blocks in your private storage. And given the addresses, use STORAGE to change it from rexx.
</good Pedro>

<evil Pedro>
You might be able to zap system storage using the TESTAUTH command. But you can easily corrupt system storage, so I do not recommend it. When they find out who crashed the system, they will be upset. TESTAUTH is usually protected from casual use.
</evil Pedro>
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dick scherrer

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PostPosted: Thu Aug 28, 2008 2:28 am
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Hello,

Quote:
But you can easily corrupt system storage, so I do not recommend it. When they find out who crashed the system, they will be upset.
Unless you have direction from your management you should not even attempt it.

Some places i've supported find this sort of "tinkering" grounds for termination. It is very likely that there is no business requirement to do this. Learning is one thing, this is more like sabotage/subtrefuge.
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angt

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PostPosted: Sat Aug 30, 2008 12:29 am
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Thanks All for your views


Pedro what is IPCS ?
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angt

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PostPosted: Sat Aug 30, 2008 1:55 am
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angt wrote:
Thanks All for your views


Pedro what is IPCS ?
I got some thing like Interactive Problem Control Fclty but I am not sure how to get control blocks in my private storage
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Pedro

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PostPosted: Sat Aug 30, 2008 5:18 am
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I suggest your application allocate a control block that includes a character field; perhaps some 8 or 16 character value that should be unique to your application. Many system control blocks typically have an 'ID' field for this purpose.

Then use IPCS to search through storage looking for your 'eyecatcher'. Then you will have the address of your control block. This is sort of a brainstorm session. I have not used IPCS in this fashion, but only surmise that it is possible.
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